In commonly owned U.S. Pat. No. 4,883,322 a mining apparatus is described for removing stratified outcropped minerals and for transporting these minerals parallel to the mining face or breast. This apparatus comprises a digging portion and a conveyor portion as well as a chain conveyor guided positively in them with digging tools and carrier members. The digging portion and the conveyor portion are assembled together from a plurality of pan-like members. Each pan of the conveyor portion comprises a conveying trough made from two guide pieces which are mirror images of each other attached to a base plate and from two identical bent plates. The guide pieces engage in members in the bent plates and are clamped with them by clamping plates on the top side of the bent plates. The digging portion has a guide piece identical with the guide piece of the conveyor portion. A basin-like plate of the digging portion is pivotably mounted by a welded substantially circular cross section strip on the breast wall side of the conveyor portion. Coupling members for the adjacent pan-like members of the conveyor portion are located under the bent plates.
Such an apparatus is typically mounted on a row of walking roof supports or props each having a floor-engaging foot, a roof-engaging head, and jack structure between them that presses the head up and the foot down to hold up the roof or hanging wall as the seam is being cut away. Such a row of walking props is lined up along to the long face wall and the props are individually pulled toward the face by respective hydraulic rams as the face is cut away to advance them and hold up the newly exposed roof. When the props are braced vertically between the roof and floor, the same rams can be used to move the mining apparatus and its conveyor forward toward the seam.
Such systems can only work over seams some 0.7 m to 1.2 m high efficiently. When the seam is taller it is necessary to use a different cutting machine or to provide an adapter for reaching the higher levels. The cutters that can work taller seams are very expensive to manufacture and cannot be used on normal-height seams, so that it they are not normally economically worthwhile.